【Passion】 ,  【fervor】 ,  【ardor】 ,  【enthusiasm】 ,  【zeal】  denote intense, high-wrought emotion.

【Passion】  implies an overwhelming or driving emotion; it may be either the most abstract or the most concrete of these terms. It may be used without implication of a specific emotion; thus, a poet without  【passion】  is a poet incapable of feeling or of displaying vehement, agitating, or soul-stirring emotion; to be in the grip of  【passion】 is to be swayed by violent emotion, but without a hint from the context the nature of the emotion remains unknown.

【Passion】 (see also FEELING  ) (see also DESIRE ) may specifically designate intense erotic love, or often lust, or it may designate violent rage.

【Fervor】  and  【ardor】  both imply the kindling of emotion to a high degree of heat, but  【fervor】  more often suggests a steady glow or burning and  【ardor】  a restless or leaping flame.  【Fervor】  is associated especially with matters (as emotions that express themselves in prayer, contemplation, or devotion) involving persistent warmth;  【ardor】 , with those (as emotions that express themselves in eager longings, or zealous efforts) that suggest the violence and sometimes the transitoriness or wavering of flames.

【Enthusiasm】  often comes very close to  【ardor】 , but it may differ in its emphasis on the rational grounds for the emotion, such as thoroughgoing admiration for a person or thing or conviction of the worthiness of a cause or end.

【Ardor】  may suggest aspiration without a clearly envisioned goal, but  【enthusiasm】  nearly always implies an objective, a cause, or an object of devotion; thus, a teacher may stimulate  【ardor】  in a pupil without necessarily directing the latter's emotion into a definite channel, but he stimulates  【enthusiasm】 only when he provides the pupil with something concrete to admire, to follow, or to fight for.

【Zeal】 retains from earlier senses a suggestion of a goading or driving 【passion】 expressed as great 【ardor】 or 【enthusiasm】 for a cause or end and coupled with energetic and unflagging activity in the service of the cause or in the pursuit of the end.